Polishing tool and device for polishing a workpiece

ABSTRACT

A polishing tool and a device for polishing a workpiece with a corresponding polishing tool are proposed, the polishing tool having an elastic intermediate layer with two portions/parts of different hardness, the portion/part close to the processing surface being softer than the portion/part of the intermediate layer remote from the processing surface.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit under 35 U.S.C. 119(a) to GermanPatent Application No. 10 2019 004 912.8, filed Jul. 16, 2019 and GermanPatent Application 10 2019 005 084.3, filed Jul. 23, 2019, thedisclosure of which are incorporated herein by reference in theirentirety.

FIELD

An exemplary aspect relates to a polishing tool and to a device forpolishing a work-piece, in particular a lens.

DESCRIPTION OF RELATED ART

A polishing tool of this type is known from German Patent Application DE10 2014 015 052 A1, corresponding to U.S. Pat. No. 10,569,387 B2. Thepolishing tool of this type has a base with a two-part foam carrierapplied to its curved front surface, which in turn carries a polishingfoil. The two-part foam carrier is softer adjacent to the base andharder adjacent to the polishing foil.

Such a polishing tool is used in particular for polishing opticalworkpieces such as lenses. Since the harder portion is much thinner thanthe softer portion, the polishing foil can adapt well to the geometry ofthe surface to be polished due to the comparatively thick softerportion. At the same time, a comparatively high removal rate can beachieved due to the comparatively thin harder area. Therefore, it shallbe possible to polish ophthalmic lenses in a range from 0 to 14 diopterswith a single tool with a constant curvature of the surface of the base.Basically, the number of polishing tools required for operating in thediopter range of the ophthalmic lenses to be polished shall be reduced.However, such a polishing tool does not meet the requirements for themost exact, deterministic polishing with a particularly accuratepolishing result.

Furthermore, numerous polishing tools with a one-piece elasticintermediate layer are known in the state of the art. In particular whencombined with a polishing spindle with spherical/ball head, the problemarises that when compressing the intermediate layer during the polishingprocess, the polishing tool or tool axis is (too) strongly deflected ortilted away from the center axis and/or drive axis (center offset). Thisleads to polishing errors because the polishing tool is not guidedcentrally and/or the tool axis is not guided perpendicular to thesurface to be polished (processing surface/target surface), butoff-center/eccentric and/or offset and/or at an angle/inclined to saidsurface.

SUMMARY

One aspect of the current technology is to improve and/or furtherdevelop a polishing tool as well as a device in such a way that aparticularly precise polishing of a work-piece, such as a lens or anophthalmic lens, is made possible, in particular with small radialdeflection of the polishing tool and/or reduced center offset during thepolishing process.

One solution to this problem is a polishing tool and a device asdisclosed herein.

A first independent aspect is that the polishing tool comprises a base,a polishing foil and/or polishing pad and a two-part or multi-partelastic intermediate layer, preferably made of foam, in particular afoam carrier, wherein the intermediate layer is designed to be harderand/or stiffer (against compression) in the (immediate) vicinity of thebase and softer and/or more elastic and/or more yielding in the(immediate) vicinity of the polishing foil. Thus, a strong radialdeflection of the polishing tool according to the invention during thepolishing process is at least reduced.

It is provided that the intermediate layer/foam carrier has a (first)portion/part in particular of foam material which (directly) adjoins thebase and/or is remote from the processing surface and a (second)portion/part in particular of foam material which (directly) adjoins thepolishing foil and/or is arranged between the polishing foil and thefirst portion/part and/or is close to the processing surface, whereinthe first portion/part is thicker, harder/less elastic, stiffer and/ordenser than the second portion/part.

Due to the softer/second portion/part, the polishing foil can adaptparticularly well to the surface of the workpiece even at highrotational speeds of the polishing tool. In particular for workpieces orlenses with surfaces which are not rotationally symmetric, such as toriclenses or free-form lenses, the arrangement according to the inventionof the portions/parts of the intermediate layer/foam carrier—in contrastto the state of the art—enables the polishing foil to dynamically adaptor snuggle against the surface so that the polishing foil always lies onthe workpiece/lens with its (entire) surface.

Due to the harder/first portion/part, the polishing tool and/or thepolishing foil can yield both in the axial direction/the direction ofthe tool axis and in the radial direction/transversely to the driveaxis, in particular to allow adaptation to height differences and/or toradii of curvature of the workpiece varying in the circumferentialdirection, as in the case of toric lenses, and/or to be able to processworkpieces with different radii of curvature with the same polishingtool.

A second independent is that a device for polishing according to theinvention comprises a—rotatably driven—tool carrier, in particular atool spindle/polishing spindle, which is (directly) connected to thebase of the polishing tool according to the invention by means of anoptional coupling element and/or is embodied for detachable and/orexchangeable holding of the polishing tool according to the invention,wherein the tool carrier, in particular the coupling element, is eitherat least substantially rigid/joint-free, in particular ball-head-free,or has an elastic flexure bearing/elastic flexure joint.

Thus, in particular, the tool carrier and/or the coupling elementdo/does not have a ball head/spherical head which would lead to anexcessive center offset of the polishing tool when the polishing tool ispressed against the workpiece and can lead to tilting during polishingin the edge area of the workpiece.

The known devices with ball head have a fixed and relatively largedistance between the joint/joint axis/tilt axis and the polishingsurface. It is therefore a constraining/coercive mechanism which, evenwith small transverse forces, leads to a large center off-set of thepolishing tool relative to the spindle axis/drive axis due to the largedistance.

In contrast, the rigid and/or joint-free device according to theinvention does not have a fixed joint axis/tilt axis.

As already explained, tilting of the polishing tool is (exclusively)caused by bending of the polishing tool, in particular of theintermediate layer/foam carrier. In other words, the polishing tool, inparticular the intermediate layer/foam carrier, preferably forms aflexure bearing, in particular with a virtual joint axis, with a reduceddistance to the polishing surface compared to known devices with ballhead, so that transverse forces of the same magnitude lead to a smallercenter offset.

The polishing tool according to one aspect, in particular thefirst/harder portion/part of the intermediate layer, can therefore takeover the compensating functions of the known ball head and enables—inparticular due to the smaller distance between the first portion/partand the polishing foil—a better guidance over/on the workpiece.

In addition, the rigid and/or joint-free device according to theinvention prevents the risk of the polishing tool lifting off theworkpiece in the edge area of the workpiece.

A basic idea according to one aspect is thus to connect the polishingtool, in particular directly and/or without a ball head, to a toolcarrier, in particular a polishing spindle. This at least reduces thecenter offset. In particular, the center offset can no longer beinfluenced by the tilting of the ball head.

A major contribution to this effect according to the invention is thatthe polishing tool according to the invention in the vicinity of thetool carrier and/or coupling element, in particular the first portion ofthe intermediate layer, is designed to be stiffer and/or harder than inthe state of the art in order to be able to contribute to a reduction ofthe center offset.

The above-mentioned aspects and features as well as the aspects andfeatures of the present invention resulting from the claims and thefollowing description can in principle be realized independently of eachother, but also in any combination.

Further aspects, advantages, features, properties and advantageousfurther developments of the present invention result from the sub-claimsand the following description of preferred embodiments with reference tothe accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic section of a device according to the inventionwith a tool carrier only partially shown and a polishing tool accordingto a first aspect;

FIG. 2 is a schematic section of the device according to FIG. 1 with thetool carrier only partially shown and the polishing tool according to afirst aspect;

FIG. 3A is a schematic section of the device according to FIG. 2 in aposition moved away from a workpiece;

FIG. 3B is a schematic section of the device according to FIG. 3A in aposition pressed against the workpiece and/or in a central processingposition;

FIG. 3C is a schematic section of the device according to FIG. 3B in aneccentric and/or deflected processing position;

FIG. 3D is a schematic section of the device according to FIG. 3C with aworkpiece rotated by 90°; and

FIG. 4 is a schematic diagram of the processing positions of thepolishing tool relative to the workpiece in a top view.

DETAILED DESCRIPTION

In the partly not to scale, only schematic figures, the same referencesigns are used for the same, identical or similar parts and components,wherein corresponding or comparable properties, characteristics andadvantages are achieved, even if a repeated description is omitted.

FIG. 1 and FIG. 2 each show one exemplary embodiment of a proposeddevice 1 for polishing a workpiece L, not shown in FIGS. 1 and 2, inparticular a lens or a spectacle/eyeglass lens.

The device 1 has a tool carrier 2, preferably rotatably driven about aspindle axis and/or drive axis A1, in particular a tool spindle and/orpolishing spindle, and a polishing tool 10 for polishing the workpieceL.

The polishing tool 10 is attached or attachable to the tool carrier 2,preferably at least substantially rigid and/or immovable and/orjoint-free.

In particular, the polishing tool 10 is detachably and/orinterchangeably attached or attachable to the tool carrier 2 so that thepolishing tool 10 preferably manually can be removed from the toolcarrier 2 after one or more polishing processes and replaced by a newpolishing tool 10.

In the embodiments shown, the polishing tool 10 according to theinvention has a base 20, an intermediate layer/foam carrier 30 and apolishing pad/polishing film/polishing foil 40.

The polishing foil 40 preferably forms a (first) axial and/or free endof the device 1 and/or the polishing tool 10. In particular, thepolishing foil 40 is in direct contact with the workpiece L whenpolishing the workpiece L.

Preferably, the polishing foil 40 has an in particular (concave orconvex) curved, particularly preferably spherical, polishing surface 41,wherein the polishing surface 41 forms a front surface of the polishingtool 10.

The intermediate layer 30 is preferably arranged between the base 20 andthe polishing foil 40. In particular, the polishing foil 40 is connectedto the base 20 by means of the intermediate layer 30.

The base 20 preferably forms a (second) axial end of the polishing tool10 and/or is (directly) connected or connectable to the tool carrier 2,as explained in more detail below.

The polishing tool 10, in particular the base 20 and/or the intermediatelayer/foam carrier 30, are/is preferably at least substantiallycylindrical and/or (each) designed as a (circular) cylinder.

Particularly preferably, the polishing tool 10 and/or the base 20 and/orthe intermediate layer 30 are/is at least essentially rotationallysymmetrical.

The tool carrier 2 is preferably rotatable about the drive axis A1,preferably wherein the drive axis A1 runs centrally through the at leastsubstantially cylindrical tool carrier 2.

The polishing tool 10, in particular the polishing foil 40, preferablyhas a tool axis A2, in particular wherein the tool axis A2 forms alongitudinal axis, symmetry axis, central axis and/or rotational axis ofthe preferably elongated and/or rotationally symmetrical polishing tool10 and/or of the preferably circular polishing foil 40.

Usually the tool axis A2 corresponds to/coincides with/is the same asthe drive axis A1. However, it is also possible to incline or tilt thepolishing tool 10, in particular the polishing foil 40, relative to thebase 20 and/or tool carrier 2 so that the tool axis A2 is inclined tothe drive axis A1, thus creating a center offset.

The spatial allocations, arrangements and/or alignments, in particularthe terms “radial” and/or “axial” used in the context of the presentinvention, preferably refer to the drive axis A1 and/or tool axis A2,unless otherwise indicated.

Preferably, the base 20 has a base part 21, a connecting part 22 and/ora head part 23, in particular wherein the base part 21 is connected tothe head part 23 by means of the connecting part 22.

The base part 21 is preferably arranged on a side of the base 20 facingthe tool carrier 2 and the head part 23 on a side of the base 20 facingaway from the tool carrier 2.

Preferably, the polishing tool 10 is attachable or attached (directly)to the tool carrier 2 by means of the base 20, in particular the basepart 21.

In the embodiments shown, the base 20 and/or the base part 21 isdesigned to at least partially receive the tool carrier 2. However,solutions are also possible in which the tool carrier 2 is designed toreceive the base 20 and/or the base part 21. For example, the toolcarrier 2 may have a bore hole to receive polishing tool 10.

Preferably, the tool carrier 2 is designed as a (tool-carrying) motorspindle and/or tool spindle and/or formed by a shaft with a toolinterface at an axial and/or free end.

Preferably the tool carrier 2, in particular the tool interface, has acoupling element/pin 80 for torque transmission.

The base 20, in particular the base part 21, preferably has a receivingregion 24 for receiving and/or centering the tool carrier 2, inparticular the coupling element/pin 80 of the tool carrier/tool spindle2.

The polishing tool 10, in particular the base 20, is connected orconnectable, preferably detachably, with the tool carrier 2, inparticular the coupling element/pin 80, by form-fit, force-fit and/oradhering/bonding.

As already explained at the beginning, the tool carrier 2/tool spindle 2is rotatably driven, preferably around the drive axis A1, for example bymeans of an electric motor (not shown).

Preferably, by means of the coupling element/pin 80 of the tool carrier2, a torque and/or a rotary movement is transmittable from the toolcarrier 2 to the polishing tool 10.

For this purpose, the coupling element/pin 80 and the receiving region24 preferably have profiles for torque transmission that arecomplementary to each other, for example polygonal profiles, so that aform-fit is created between the tool carrier 2 and the polishing tool 10in the direction of rotation when the coupling element/pin 80 isinserted into the receiving region 24, as shown in FIGS. 1 and 2.

Preferably, the base 20, in particular the base part 21, liesaxially—and optionally also radially—against the tool carrier 2 with itssurface.

Preferably, the base 20, in particular the base part 21, has a base partsurface 25, which lies axially and/or radially against a correspondingsupport surface 3 of the tool carrier 2.

As already explained, the polishing tool 10 is detachably connected orconnectable to the tool carrier 2. Preferably, the device 1 and/or toolcarrier 2 has a coupling for detachably connecting the polishing tool 10to tool carrier 2.

In the embodiment shown in FIG. 1, the device 1 and/or the tool carrier2 is equipped with a pneumatically actuated coupling, in which a sealingring 4 can be acted upon with pressurized air via a central and/oraxially running supply line 5 and one or more radially running pressurelines 6 in such a way that the sealing ring 4 can be pressed radiallyagainst the polishing tool 10 and/or the base 20. In this way, africtional/force-fit connection is produced between the tool carrier 2and the polishing tool 10.

In the embodiment shown in FIG. 2, the device 1 and/or tool carrier 2 isequipped with a magnetic coupling to magnetically connect the polishingtool 10 to tool carrier 2. For this purpose, the polishing tool 10 hasone or more magnets 26 which are embedded in the base 20 and/or the basepart 21 to allow magnetic adhesion to the preferably metallic toolcarrier 2.

Preferably, the base 20 is designed to be rigid and/or harder, stifferand/or less elastic than the intermediate layer 30 and/or the polishingfoil 40, in particular to give the polishing tool 10 the necessarystability and/or to allow/enable attachment to the tool carrier 2.

The base 20 is preferably designed/constructed in one piece and/or madeof a suitable plastic material, e.g. rigid PVC (PVC-U), in a mannerknown per se, in particular (injection-)molded.

The base 20, in particular the head part 23, is preferably designed tohold the intermediate layer/foam carrier 30, in particular in such a waythat the rotary movement and/or the torques can be transmitted to theintermediate layer/foam carrier 30.

For this purpose, the intermediate layer/foam carrier 30 is connected tothe base 20, in particular the head part 23, by form-fit, force-fitand/or adhering/bonding.

In some of the exemplary embodiments shown, the intermediate layer/foamcarrier 30 and the base 20 are adhered together as indicated by abonded/adhesive seam and/or an adhesive layer 50.

The base 20, in particular the head part 23, has a front surface 27facing the intermediate layer/foam carrier 30, preferably wherein theintermediate layer/foam carrier 30 is adhered to the front surface 27.

As already explained, the polishing tool 10 and/or polishing foil 40 hasthe polishing surface 41, by means of which the workpiece L and/or thetarget surface/processing surface LF of the workpiece L can be polished.

The polishing surface 41 is preferably curved, especially preferablyconvex or concave, in particular spherical, preferably toprocess/machine the correspondingly curved processing surface LF of theworkpiece L.

Preferably, the surface and/or front surface 27 of the base 20 iscurved, particularly preferably convex or concave, in particularspherical, preferably in order to bend/curve the intermediate layer/foamcarrier 30 and/or to create the curvature of the polishing surface 41 inthis way. In this way, it is possible to dispense with a relativelyexpensive adaptation of the intermediate layer/foam carrier 30 and touse plate-shaped parts.

Preferably the radius of curvature of the front surface 27 of the base20 is at least 75 mm and/or at most 1000 mm, particularly preferably atleast substantially 150 mm or 600 mm.

Preferably, the radius of curvature of the polishing surface 41 islarger than the radius of curvature of the front surface 27, preferablyby at least 100 mm, depending on the thickness and material propertiesof the intermediate layer/foam carrier 30 and the polishing foil 40.

In comparison to the state of the art, larger radii of curvature of thefront surface 27 and/or the polishing surface 41 have proven to beeffective in order to be able to process larger processing surfaces LFand/or to increase the removal during polishing.

Particularly preferably, the radius of curvature of the polishingsurface 41 is larger than the (largest) radius of curvature of theworkpiece L in order to create an annular contact surface when pressingthe polishing tool 10 onto the workpiece L. This is an advantageous wayto increase the removal rate in comparison with punctiform contactsurfaces and/or small radii of curvature of the polishing surface 41.

As already explained at the beginning, the intermediate layer/foamcarrier 30 is made up of multiple parts and/or layers and/or is formedby a plurality of portions and/or parts.

The intermediate layer/foam carrier 30 has two parts/layers in theembodiments shown. However, solutions are also possible in which theintermediate layer/foam carrier 30 is composed of more than two portionsand/or parts and/or layers.

Preferably, the intermediate layer/foam carrier 30 has a firstportion/part 31 and a second portion/part 32.

The first portion/part 31 adjoins (directly and/or axially) the base 20.In particular, the first portion/part 31 is (directly) attached to thebase 20 and/or adhesively bonded with the base 20 and/or (axially)arranged between the second portion/part 32 and the base 20.

The second portion/part 32 adjoins (directly and/or axially) thepolishing foil 40. In particular, the polishing foil 40 is (directly)attached to and/or adhesively bonded with the second portion/part 32and/or the second portion/part 32 is (axially) arranged between thefirst portion/part 31 and the polishing foil 40.

Preferably, the material properties and/or the geometry and/or thestructural design of the portions/parts 31 and/or 32 differ from eachother.

The essential aspect of the invention is that the first portion/part 31and/or the portion/part 31 facing the base 20 is harder and/or lesselastic and/or stiffer (than the second portion/part 32) and that thesecond portion/part 32 and/or the portion/part 32 facing the polishingfoil 40 is softer and/or more elastic and/or more pliable and/or moreflexible (than the first portion/part 31).

According to one aspect, these properties/characteristics are preferablyto be understood in such a way that the static and/or dynamic modulus ofelasticity is higher in the vicinity of the base 20 than in the vicinityof the polishing foil 40 and/or, conversely, that the static and/ordynamic modulus of elasticity is lower in the vicinity of the polishingfoil 40 than in the vicinity of the base 20.

Thus, preferably, the—static and/or dynamic—modulus of elasticity of thefirst/harder portion/part 31 is greater than the—static and/ordynamic—modulus of elasticity of the softer/second portion/part 32,preferably by at least a factor of 1.2 or 1.5 or 2.

Preferably, the first/harder portion/part 31 has a (static) modulus ofelasticity of more than 0.4 N/mm², particularly preferably more than0.75 N/mm², and/or less than 2 N/mm², particularly preferably less than1.75 N/mm².

Preferably, the softer/second portion/part 32 has a (static) modulus ofelasticity of more than 0.05 N/mm² or 0.075 N/mm², in particular morethan 0.1 N/mm², and/or less than 1 N/mm² or 0.9 N/mm², in particularless than 0.8 N/mm² or 0.6 N/mm².

The modulus of elasticity is preferably a material characteristic valuefor the relationship between stress and strain and/or pressure andcompression when a (test) piece made of this material is deformed.

A material with a low modulus of elasticity is softer and/or moreelastic and/or easier to compress than a material with a higher modulusof elasticity.

The terms “hard” and/or “soft” are to be understood as a materialproperty which can be used as a measure of the force required tocompress or squeeze the material by a certain length value.

In other words, the “hardness” and/or “softness” and/or “stiffness” isthe mechanical resistance that a material and/or substance has against(elastic) deformation/compression.

A hard material is preferably less elastic and/or less easy to compressthan a soft material.

The term “elasticity” and/or “elastic” in the sense of the presentinvention is preferably understood to mean the property of a material tochange its shape elastically, i.e. not plastically, under the action offorce and to return to its original shape—without permanentdeformation—when the acting force is removed.

To determine the (static) modulus of elasticity, a predefined pressureis preferably applied to a surface of a cuboidal, in particular acube-shaped, test piece and the compression of the test piece in thedirection of pressure/force is measured.

The modulus of elasticity is preferably the quotient of pressure in[N/mm²] and compression in [mm] multiplied by the original length/widthin [mm] of the test piece in the direction of pressure/force.

Preferably, the above values for the modulus of elasticity refer to atest piece in which the ratio of the pressurized surface to the lateralsurface (shape factor/form factor) is three and to which a pressure of0.01 N/mm² or 0.035 N/mm² or 0.055 N/mm² or 0.1 N/mm² or 0.2 N/mm² isapplied.

Preferably, the first/harder portion/part 31 has a greater compressionhardness than the second/softer portion/part 32, in particular by atleast a factor of two, three or four.

Preferably, the compression hardness of the first/harder portion/part 31is at least 0.05 N/mm², 0.1 N/mm² or 0.12 N/mm² and/or at most 0.3 N/mm²or 0.2 N/mm².

Preferably, the compression hardness of the first/harder portion/part 31is at least essentially 0.15 N/mm².

Preferably, the compression hardness of the second/softer portion/part32 is at least 0.01 N/mm² or 0.02 N/mm² and/or at most 0.1 N/mm² or 0.08N/mm².

Preferably, the compression hardness of the second/softer portion/part32 is at least essentially 0.031 N/mm² or 0.047 N/mm².

The compression hardness is preferably a material characteristic valuethat indicates the force required to compress a test piece by a certainlength.

The above values for the compression hardness preferably refer to acuboidal, in particular a cube-shaped, test piece in which the ratio ofthe pressurized surface to the lateral surface (shape factor/formfactor) is three and which has been compressed by 10% relative to itsoriginal size.

Additionally or alternatively, the geometry and/or structural design ofthe first portion/part 31 may differ from the second portion/part 32, inparticular to achieve different stiffness.

For example, the second portion/part 32 can be provided with recesses,such as slots, holes, bores or the like. In this way, the stiffness ofthe second portion/part 32 can be reduced—even with otherwise identicalmaterial properties—compared to the first portion/part 31.

The intermediate layer/foam carrier 30 is preferably (exclusively)formed by or made of foam, in particular polyurethane foam.

The first/harder portion/part 31 is preferably (exclusively) made of aclosed-cell foam, in particular a closed-cell polyurethane foam.

The softer/second portion/part 32 is preferably (exclusively) made of anopen-cell, mixed-cell or closed-cell foam, in particular an open-cell,mixed-cell or closed-cell polyurethane foam.

In the case of closed-cell foams, the walls between the individual cellsof the foam are—at least substantially—closed, in particular in such away that there is no exchange of liquid between the cells and/or thefoam cannot absorb liquid. Preferably, a closed-cell foam has more than80% or 90% closed cells and/or less than 20% or 10% open cells.

In the case of open-cell foams, the walls between the individual cellsof the foam are at least partially open or not closed, in particular insuch a way that a liquid exchange can take place between the cellsand/or the foam can absorb liquid. Preferably, an open-cell foam hasmore than 70% or 80% open cells and/or less than 30% or 20% closedcells.

In the case of mixed-cell foams, the walls between the individual cellsof the foam are partially open and partially closed. In particular, amixed-cell foam is a mixture of a closed-cell foam and an open-cellfoam. Preferably, the amount of open and/or closed cells in a mixed-cellfoam lies between the amount for a closed-cell foam and an open-cellfoam.

Usually, closed-cell foams are harder than open-cell and/or mixed-cellfoams. Against this background, closed-cell foams are preferred for thefirst portion/part 31 and open-cell and/or mixed-cell foams for thesecond portion/part 32. However, it is also possible to use aclosed-cell foam for the second portion/part 32 if correspondingmaterial properties are achieved as with an open-cell or mixed-cellfoam.

The absorption of polishing agent can affect the material properties ofthe foam.

To prevent or at least reduce the influence of the polishing agent onthe material properties, it is preferable to use a closed-cell ormixed-cell foam also for the softer/second portion/part 32.

Preferably, the first/harder portion/part 31 and the second/softerportion/part 32 are connected with each other by adhering/boding.

As indicated by a corresponding adhesive seam and/or adhesive layer 60,the portions/parts 31, 32 are adhered together in the embodiments shown.However, it is also possible to foam the two portions/parts 31, 32together during production.

It is preferred—in contrast to the state of the art—that the harderportion/part 31 is (significantly) thicker than the softer portion/part32, in particular to enable precise polishing by means of the polishingtool 10 and to reduce the center offset, as explained at the beginning.

Preferably, the first/harder portion/part 31 is at least by a factor of1, 1.1 or 1.5 and/or at most by a factor of 3 or 2 thicker than thesecond/softer portion/part 32.

Preferably, the axial extension and/or thickness D1 of the first/harderportion/part 31 is at least 5 mm or 6 mm, particularly preferably atleast 8 mm or 10 mm, and/or at most 20 mm or 18 mm, particularlypreferably at most 16 mm or 14 mm.

Preferably, the axial extension and/or thickness D2 of the second/softerportion/part 32 is at least 2 mm or 4 mm, particularly preferably atleast 6 mm, and/or at most 12 mm or 10 mm, particularly preferably atmost 9 mm.

Preferably, the axial extension and/or thickness of the intermediatelayer/foam carrier 30 in total is at least 12 mm or 14 mm, particularlypreferably at least 15 mm, and/or at most 30 mm or 25 mm, particularlypreferably at most 22 mm or 20 mm.

As already explained, the intermediate layer/foam carrier 30 iscylindrical and/or embodied as a (circular) cylinder. Preferably, theintermediate layer/foam carrier 30 has an at least essentially constantdiameter along the tool axis A2 and/or in the axial direction.

Preferably, the diameter of the intermediate layer/foam carrier 30 is atleast 35 mm and/or at most 60 mm.

Preferably, the diameter of the polishing foil 40 is larger than thediameter of the intermediate layer/foam carrier 30. In other words, thepolishing foil 40 preferably protrudes at the edges beyond theintermediate layer/foam carrier 30.

Preferably, the polishing foil 40 is connected to the intermediatelayer/foam carrier 30, in particular the second/softer portion/part 32,by bonding, in particular adhering, as indicated by a correspondingadhesive seam and/or adhesive layer 70 in the figures.

The polishing foil 40 preferably has a thickness D3 of at least 0.08 mmor 1 mm and/or at most 2 mm, particularly preferably at leastsubstantially 1.2 mm.

The polishing foil 40 is preferably made of polyurethane.

As already explained, the device 1 and/or the polishing tool 10 isdesigned for (micro)cutting/machining/processing (of surfaces), inparticular for fine processing and/or polishing, of the workpiece Land/or the processing surface LF of the workpiece L.

The processing/machining and/or the polishing process of the workpiece Lwill be explained in more detail below with reference to FIG. 3A to 3Dand FIG. 4.

FIG. 3A shows the device 1 and/or polishing tool 10 in a position(moved) away from the workpiece L. FIG. 3B shows the device 1 and/orpolishing tool 10 in a position pressed against the workpiece L and/orin a (central) processing position in which the polishing tool 10 andthe workpiece L are arranged coaxially. FIG. 3C shows the device 1and/or polishing tool 10 in an eccentric/off-center and/or deflectedprocessing position. FIG. 3D shows the device 1 and/or polishing tool 10in the eccentric/off-center and/or deflected processing positionaccording to FIG. 3C with workpiece L rotated by 90° about a workpieceaxis A3. FIG. 4 shows a schematic view/diagram of possible processingpositions of the device 1 and/or polishing tool 10 relative to theworkpiece L.

In the processing/machining position and/or during the polishingprocess, the polishing tool 10, in particular the polishing foil 40, andthe workpiece L are in contact with each other. In particular, in theprocessing position and/or during the polishing process, the polishingsurface 41 lies preferably with its (entire) surface on the workpiece Land/or the processing surface LF, as shown in FIGS. 3B, 3C and 3D.

Preferably, a polishing force and/or polishing pressure and/orcontact/surface pressure is applied to the workpiece L during thepolishing process.

Preferably, the polishing pressure is kept at least essentially constantduring a polishing process.

Preferably, during the polishing process, a polishing pressure of morethan 0.01 N/mm² or 0.02 N/mm² and/or less than 1 N/mm² or 0.05 N/mm², inparticular less than 0.1 N/mm², is generated and/or applied to theworkpiece L.

In the processing position and/or during the polishing process, thepolishing tool 10, in particular the intermediate layer/foam carrier 30,is compressed/squeezed, preferably wherein the second/softerportion/part 32 is compressed/squeezed more than the first/harderportion/part 31.

Particularly preferably, the intermediate layer/foam carrier 30 iscompressed/squeezed by more than 5% or 10% and/or by less than 80%, inparticular less than 50% or 25% (based on the original thickness of theintermediate layer/foam carrier 30).

As already explained, the workpiece L is preferably a lens, inparticular a spectacle lens.

Preferably, the workpiece L is round in a top view and/or designed as a(circular) cylinder.

In particular, the workpiece L has a workpiece axis A3, wherein theworkpiece axis A3 forms a central axis and/or rotational axis of theworkpiece L.

The workpiece L preferably has a larger diameter than the polishing tool10 and/or the polishing foil 40, in particular by at least a factor of1.2 or 1.5, particularly preferably by at least a factor of 2. However,it is also possible that the diameter of the workpiece L is at leastsubstantially the same as the diameter of the polishing foil 40.

For the processing and/or the polishing process, the workpiece L ispreferably fixed/attached to a workpiece carrier (not shown), inparticular by means of a block piece (not shown).

Preferably, the workpiece L rotates during the processing and/or thepolishing process and/or the workpiece carrier is rotatably driven, forexample by means of an electric motor (not shown).

Preferably, the rotational speed of the polishing tool 10 and/or toolcarrier 2 is greater than the rotational speed of the workpiece L and/orworkpiece carrier, particularly preferably by at least a factor of 1.5or 2. However, it is also possible that the rotational speed of thepolishing tool 10 is at least substantially the same as the rotationalspeed of the workpiece L.

Preferably, the rotational speed of the polishing tool 10 and/or toolcarrier 2 and/or workpiece L is more than 1000 min⁻¹ or 1200 min⁻¹, inparticular at least essentially 1500 min⁻¹ or 2000 min⁻¹.

Preferably, the workpiece L rotates in the opposite direction topolishing tool 10, as indicated by the corresponding arrows in FIG. 4.However, a rotation of workpiece L and polishing tool 10 in the samedirection is also possible.

A polishing process in the sense of the present invention means inparticular the complete polishing of the processing surface LF to bepolished of the workpiece L with the polishing tool 10.

Preferably, the duration of a (complete) polishing process is between 30seconds and 120 seconds.

Particularly preferably, a plurality, in particular at least 100 or 150,of polishing processes can be carried out and/or of workpieces L can beprocessed with the polishing tool 10 before a change of the polishingtool 10 is necessary.

For the processing and/or the polishing process, the workpiece L and thepolishing tool 10 are preferably (initially) aligned coaxially with eachother and/or aligned with each other in such a way that the tool axis A2corresponds to/coincides with/is the same as the workpiece axis A3and/or that the polishing surface 41 is arranged directly opposite toand/or centrally on the processing surface LF of the workpiece L, asshown in FIG. 3A.

Then the polishing tool 10 and the workpiece L are pressed together, asshown in FIG. 3B.

During the (subsequent) processing and/or during the polishing process,the polishing tool 10 and the workpiece L are moved relative to eachother—in particular radially and/or axially—in particular in order toprocess the entire processing surface LF of the (larger) workpiece Lwith the (smaller) polishing tool 10.

Preferably, the polishing tool 10 and the workpiece L are moved radiallyrelative to each other, in particular in such a way that the drive axisA1 and/or the tool axis A2 is (radially) offset and/or shifted and/ortilted relative to the workpiece axis A3.

The tool carrier 2 and thus the polishing tool 10 are preferablyadjustable in an X-direction and/or along an X-axis, in particular bymeans of a slide (not shown) and an associated drive (not shown).

The X-axis is preferably designed as a controlled or feedback-controlledaxis and/or as a CNC-axis or linear axis, so that precise positioning inthe X-direction is made possible.

Preferably, the X-axis is transverse and/or perpendicular to the driveaxis A1, the tool axis A2 and/or the workpiece axis A3.

It is further provided that the tool carrier 2 and thus the polishingtool 10 is pivotable about a swivel axis B, hereinafter referred to asB-axis, in particular about a swivel angle S, as shown in FIG. 3C.

The B-axis is preferably designed as a controlled or feedback-controlledswivel axis and/or CNC axis, also called rotary axis.

Preferably, the B-axis is transverse, in particular at leastsubstantially perpendicular, to the X-axis, drive axis A1, tool axis A2and/or workpiece axis A3, as indicated in FIG. 4.

By swiveling the polishing tool 10, it is possible to follow thecurvature of the processing surface LF and/or to provide a large contactsurface also in the edge area of the processing surface LF and thus ahigh removal rate.

In addition, by swiveling the polishing tool 10, the polishing forceand/or polishing pressure is not or not significantly changed when thepolishing tool 10 is guided/moved to the edge area of the processingsurface LF.

It is thus preferable to move the (smaller) polishing tool 10—inparticular by shifting/moving it along the X-axis and/or swiveling itaround the B axis—from the center to the edge of the (larger) workpieceL (or vice versa) in order to polish the entire processing surface LF,as indicated in FIG. 4.

As already explained, the polishing tool 10 and/or the polishing foil 40can give way/yield in the radial direction and/or transverse to thedrive axis A1, for example to allow adaptation to radii of curvature ofthe workpiece L that change in the circumferential direction, as in thecase of toric lenses.

In FIG. 3D, the workpiece L is rotated by 90° about the workpiece axisA3 compared to FIG. 3C, the radius of curvature of the workpiece L inthe sectional plane shown in FIG. 3D being smaller than that shown inFIG. 3C.

The smaller radius of curvature results in the polishing tool 10, inparticular the intermediate layer 30, being more strongly compressed inthe deflected and/or eccentric/off-center processing position at theedge of workpiece L, in FIG. 3D on the right, than in the center of theworkpiece L. This results in the workpiece axis A3 being tilted relativeto the drive axis A1 and a center offset being created.

Due to the construction of the device 1 and/or the polishing tool 10according to the invention and/or due to the rigid/stiff and/orjoint-free construction of the device 1 and/or the polishing tool 10, itis possible to move the polishing tool 10 and/or the tool axis A2 up toor over the edge of the workpiece L without the polishing foil 40lifting off the processing surface LF. On the contrary, known deviceswith a joint, such as a ball/spherical head, would tilt in a processingposition in which the tool axis A2 is moved over the edge of theworkpiece L in such a way that the polishing foil 40 would lose contactwith the processing surface LF.

With the polishing tool 10 according to the invention, it is thereforepossible to carry out surface polishing and/or polishing with a highremoval rate even in the edge area of the workpiece L.

As can be seen from FIGS. 1 and 2, a device 1 for polishing according tothe invention has a tool carrier 2, in particular a polishing spindle,which is rigidly connected to the base 20 of the polishing tool 10according to the invention, in particular by means of the couplingelement 80, in particular by the coupling element 80 itself being rigid.The coupling element 80 thus has in particular no ball head which wouldcontribute to an excessive center offset of the polishing tool 10according to the invention. Rigid connections between a polishing tool10 and a tool carrier 2 are known per se in the state of the art.

In an alternative embodiment (not shown), a device 1 for polishingaccording to the invention has a tool carrier 2, in particular apolishing spindle, which is elastically connected to the base 20 of thepolishing tool 10 according to the invention by means of the couplingelement 80, wherein the coupling element 80 is designed in the form ofan elastic flexure bearing/elastic flexure joint. Such connections bymeans of elastic flexure bearings are known per se in the state of theart.

A basic idea according to one aspect is to connect the polishing tool 10according to the invention to the tool carrier 2, in particular apolishing spindle, joint-free/without a ball head. This at least reducesthe center offset. In particular, the center offset can no longer beinfluenced by the tilting of a ball head.

A major contribution to this effect according to the invention is thatthe polishing tool 10 according to the invention in the vicinity of thecoupling element 80 and/or the first portion/part 31 of the intermediatelayer 30 is designed to be stiffer and/or harder and preferably alsothicker than in the state of the art in order to be able to contributeto a reduction of the center offset.

Further aspects which are realizable independently but also incombination with the aspects explained above are in particular:

1. Polishing tool, comprising:

a base 20,

an elastic intermediate layer 30, in particular a foam carrier, appliedto the base 20, a polishing foil 40 applied to the elastic intermediatelayer 30, wherein the elastic intermediate layer 30 has at least twoportions 31, 32 of different hardness,

characterized

in that the portion 31 of the elastic intermediate layer 30 adjoiningthe base 20 is harder than the portion 32 of the elastic intermediatelayer 30 adjoining the polishing foil 40.

2. Polishing tool according to aspect 1, characterized in that theharder portion 31 of the elastic intermediate layer 30 has a degree ofdeformation of 7% to 75% at a compressive load of 0.028 N/mm² to 1N/mm².

3. Polishing tool according to aspect 1 or 2, characterized in that theratio of the thickness D1 of the harder portion 31 to the thickness D2of the softer portion 32 of the elastic intermediate layer 30 is 2:1 to1:1, in particular 3:2 to 1:1.

4. Polishing tool according to one of the preceding aspects,characterized in that the harder portion 31 is made of a closed-cellfoam.

5. Polishing tool according to aspect 4, characterized in that theharder portion 31 consists of a closed-cell polyetherurethane foam.

6. Polishing tool according to one of the preceding aspects,characterized in that the harder portion 31 has a compressive strengthof up to 0.120 N/mm².

7. Polishing tool according to one of the preceding aspects,characterized in that the harder portion 31 has a static shear modulusof 0.07 N/mm² to 0.13 N/mm².

8. Polishing tool according to one of the preceding aspects,characterized in that the harder portion 31 has a dynamic shear modulusof 0.15 N/mm² to 0.18 N/mm².

9. Polishing tool according to one of the preceding aspects,characterized in that the harder portion 31 is adhered to the base 20and/or the softer portion 32 is adhered to the polishing foil 40.

10. Device for polishing a workpiece, having a tool carrier, inparticular a polishing spindle, which is connected by means of acoupling element to the base of a polishing tool 10 according to one ofaspects 1 to 9, the coupling element 80 being either rigid or in theform of an elastic flexure bearing.

Individual aspects and features of the present invention can be realizedindependently of each other, but also in any combination.

LIST OF REFERENCE SIGNS

1 Device

2 Tool Carrier

3 Support Surface

4 Sealing Ring

5 Supply Line

6 Pressure Line

10 Polishing Tool

20 Base

21 Base Part

22 Connecting Part

23 Head Part

24 Receiving Region

25 Base Part Surface

26 Magnet

27 Front Surface

30 Intermediate Layer/Foam Carrier

31 First/Harder Portion/Part

32 Second/Softer Portion/Part

40 Polishing Foil

41 Polishing Surface

50 Adhesive Seam between Base and Intermediate Layer

60 Adhesive Seam between First and Second Portion/Part

70 Adhesive Seam between Intermediate Layer and Polishing Foil

80 Coupling Element/Pin

A1 Drive Axis

A2 Tool Axis

A3 Workpiece Axis

B Swivel Axis

D1 Thickness of the First/Harder Portion/Part

D2 Thickness of the Second/Softer Portion/Part

D3 Thickness of the Polishing Foil

L Workpiece

LF Processing Surface

S Swivel Angle

X Linear Axis

What is claimed is:
 1. A polishing tool comprising: a base, an elasticintermediate layer applied to the base, a polishing foil applied to theintermediate layer, wherein the intermediate layer has at least twoportions of at least one of different hardness or stiffness, wherein afirst portion of the intermediate layer adjoining the base is at leastone of harder or stiffer than a second portion of the intermediate layeradjoining the polishing foil.
 2. The polishing tool according to claim1, wherein the intermediate layer is a foam carrier.
 3. The polishingtool according to claim 1, wherein the modulus of elasticity of thefirst portion is greater than the modulus of elasticity of the secondportion.
 4. The polishing tool according to claim 1, wherein the modulusof elasticity of the first portion is at least one of more than 0.4N/mm² or less than 2 N/mm².
 5. The polishing tool according to claim 1,wherein the modulus of elasticity of the second portion is at least oneof more than 0.05 N/mm² or less than 1 N/mm².
 6. The polishing toolaccording to claim 1, wherein the first portion is thicker than thesecond portion.
 7. The polishing tool according to claim 6, wherein thefirst portion is at least twice as thick than the second portion.
 8. Thepolishing tool according to claim 1, wherein the ratio of the thicknessof the first portion to the thickness of the second portion of theintermediate layer is at least one of the following: at least 3:2, atleast 2:1, at most 1:2, or at most 2:3.
 9. The polishing tool accordingto claim 1, wherein the first portion consists, comprises or is made ofa closed-cell foam.
 10. The polishing tool according to claim 1, whereinthe second portion consists, comprises or is made of an open-, mixed- orclosed-cell foam.
 11. The polishing tool according to claim 1, whereinthe base has a curved front surface, the radius of curvature of thefront surface being at least one of at least 50 mm or at most 1000 mm.12. The polishing tool according to claim 1, with at least one of thefirst portion being adhered to the base or the second portion beingadhered to the polishing foil.
 13. The polishing tool according to claim1, wherein the second portion has one or more recesses.
 14. A deviceconfigured to polish a workpiece, having a rotatably driven tool carrierand a polishing tool, wherein the polishing tool is replaceably attachedto the tool carrier, wherein the polishing tool comprises a base, anelastic intermediate layer applied to the base, and a polishing foilapplied to the intermediate layer, wherein the intermediate layer has atleast two portions of at least one of different hardness or stiffness,wherein a first portion of the intermediate layer adjoining the base isat least one of harder or stiffer than a second portion of theintermediate layer adjoining the polishing foil.
 15. The deviceaccording to claim 14, wherein the tool carrier is at least one of rigidor joint-free.
 16. The device according to claim 14, wherein the toolcarrier has an elastic flexure bearing.
 17. The device according toclaim 14, wherein the first portion is at least twice as thick than thesecond portion.
 18. The device according to claim 14, wherein the ratioof the thickness of the first portion to the thickness of the secondportion of the intermediate layer is at least one of the following: atleast 3:2, at least 2:1, at most 1:2, or at most 2:3.
 19. The deviceaccording to claim 14, wherein the first portion consists, comprises oris made of a closed-cell foam.
 20. The device according to claim 14,wherein the second portion consists, comprises or is made of an open-,mixed- or closed-cell foam.